A guidewire is used to guide a catheter in a medical treatment to a site having a surgical difficulty, or a medical treatment aiming to minimize injury to a human body, such as percutaneous transluminal coronary angioplasty (PTCA), for example, and a medical examination such as cardiovascular radiography. The guidewire used for PTCA is inserted into the vicinity of an angiostenosis portion, which is the target site, together with a balloon catheter in a state where a distal end of the guidewire is protruded from a distal end of the balloon catheter. The guidewire guides a distal end portion of the balloon catheter to the vicinity of the angiostenosis portion.
In percutaneous transluminal angioplasty (PTA), which is substantially similar to PTCA, the distal end portion of the balloon catheter is guided to the vicinity of the angiostenosis portion by using the guidewire to open a stenosis portion (closed portion) formed in a peripheral blood vessel such as femoral, iliac, renal, and shunt blood vessels.
The blood vessels to which these medical treatment methods are applied are intricately curved. Therefore, the guidewire used when the balloon catheter is inserted into the blood vessel requires flexibility and resilience for moderate bending, pushing performance and torque transmission performance (these are generically referred to as “operability”) for transmitting an operation in a proximal end portion to a distal end thereof, and also kink resistance (bending resistance).
Known guidewires have a first wire made of a Ni—Ti-based alloy and a second wire made of stainless steel (for example, refer to JP-A-2008-161589). In the guidewire disclosed in JP-A-2008-161589, a guidewire is provided in which a proximal end surface of the first wire and a proximal end surface of the second wire are joined to each other to form a joint portion, and the joint portion is covered with a coil from an outer peripheral side thereof. When this guidewire is used, there is a possibility that the following situations may occur depending on the magnitude of an operator's operating force.
For example, the first wire and the second wire have considerably different rigidity. Consequently, there is a possibility that the wires in the joint portion are unintentionally bent or, on the other hand, the joint portion is caused to have a rigidity much stronger than that of the leading and trailing portions thereof, and thus the joint portion is unlikely to be curved along the curves of the blood vessel.
In addition, in the guidewire disclosed in JP-A-2008-161589, a guidewire is also disclosed in which a proximal end portion of the first wire and a proximal end portion of the second wire are connected to each other via a pipe. When this guidewire is used, depending on the magnitude of the operator's operating force, there is a possibility that the rigidity of a portion between the first wire and the second wire becomes very strong in the pipe, and thus the guidewire is unlikely to be curved.